Just wunderin what it would change my gearing to from going from stock 265/17/70 goodyear wranglers to 285/17/70 Cooper ATRS. I remeber when I first drove it with the new tires...I could feel the loss in power. But after a couple days I got used to it. are gears expensive? on my original window sticker it said the 3.92 was only a extra $35 option..LOL

 

Your original tires were 31.6" tall, your new tires are 32.7" tall, effectively changing the ratio of your stock 3.92 gears to 3.78...

A change to 4.56s would feel better than the 3.92's with the stock tires. The gears and bearing kit are relatively inexpensive, especially for the performance gains, the problem, however is the labor ain't so cheap...

 

As hammer said gears aren't that expensive but labor costs suck. Since your only running 285's, it'd would be cheaper to pick up a programmer/chip and it'd probably make you forget about the change in tire size. I'm running 285's with 3.92 gears and the Superchips flashpaq 3815 and I love the way my truck runs. Now of course I should justify that in I was running a '98 Ram with a 5.2L with 3.55 gears and a Superchips 3715, so the Hemi with 120 more stock hp is quite the jump up in performance, but the truck is still night and day difference with the Superchips on it compared to not.

 

It means a reduced mechanical advantage when turning the wheel. The larger the outside diameter of the wheel, the more force is lost.

To keep the force constant you have to go with shorter gears.

 

Taller tires have less Revolutions per mile therefore, they turn slower, acting as if the gear ratio was numerically smaller.
My 88 5.0 Mustang has 3.55 gears in it with 26" tall tires.
My old F150 that I had had 3.55 gears with 31.7" tall tires.
The Mustang acts like it has a much lower gear then the truck did due to the tire diameter.

 

Oh and for the record, they are 285/70/17 tires.

285mm wide, 70% as tall as they are wide(aspect ratio) and use a 17" rim.

 

Your truck comes from the factory with the optimum (hopefully) axle gear ratio to work with the truck's engine, transmission, and stock tire combination as well as provide a good balance between acceleration and fuel economy. When taller tires are installed on a truck but the axle ratios stay the same; the effective gear ratio is reduced. This means the engine is forced to operate below its power band, and performance and fuel economy suffer as a result. In order to restore the effective gear ratio (and the truck's performance), you'll need to have the axle gears swapped to lower (numerically higher) ratios. Fortunately, finding the correct gear ratio to run with the tires that you plan to install is simple using a mathematical formula. This formula is as follows:

Effective Gear Ratio = Original Tire Size/New Tire Size X Axle Gear Ratio

Edit: Italicized because it is a cut & paste, not my words - I'm not that smart...

And I do agree with you on one point, 4.10s would be a great FINAL gear ratio, ultimate ratio for a balance of performance and economy is considered to be right around 4.25, however after the addition of 33" tires he would be at an effective ratio of about 3.9 after installing 4.10 gears, but he would be just slightly over 4.3 after the addition of 4.56 gears.

 

And you base this statement on what fact? Can you provide a document from a creditable source as to what the perfect gear ratio is. KRC Performance recommends 4.56 for any truck that is a QC with an overdrive transmission. Air Ram recommends 4.56 for ANY Dodge truck, even with stock tires. And your claim to fame in the Dodge Performance profession is what?

When I give an opinion, unless it is documented or I've gotten it from what I consider a creditable source, I usually state that it is simply my opinion. You seem to state things as fact, so I would like to know what you base this statement on?

With that said, based on my own personal experience with gears and from the recommendations I've either gotten first hand or read, it is my opinion that the proper gears to go with in his case would be 4.56's.

 

Nothing in the field, anymore anyway. I used to work with the old man in the pits at a small racetrack when I was a teen and was a mechanic at a Chrysler dealership between high school and college. Not much engine work, I was always kinda known around my town as the "lift guy" and did mostly suspension work at the dealership and any welding that needed to be done. I've done a lot of small engine, ATV, & Outboard repair for a dealership after I got out of technology (the first time) in the early '90s.
That's why I tend to hang at performance shops, I do almost all my own work, but have been out of touch for a long time and try to absorb as much information as I can before I f*ck something up. It's just interesting to me that your opinions are so different from the information I pick up from them, the more performance oriented forums and in some cases, even my own experiences. That's like on the post about going from synthetic back to dino oil. You are the ONLY person (mechanic) or otherwise who I've ever heard make the statement that you cannot. I noticed when I furnished proof you demanded that you can at any time without having to do anything special, as per MOBIL OIL, you didn't post in that thread anymore. No offense meant, but it kinda gave me the opinion that you didn't know wtf you were talking about...

 

tire size also affects gearing on atvs say 14teeth front drive with a 36teeth rear drive with 18inch tires then if i was to put 22inch tires on the back it would be the same as adding
3 or 4 teeth in the back or 1 t up front